title: Proteolysis of the type III glutamine synthetase from Bacteroides fragilis causes expedient crystal-packing rearrangements.
abstract: This work details the intentional modifications that led to the first structure of a type III glutamine synthetase enzyme (GSIII). This approach followed the serendipitous discovery of digestion caused by an extracellular protease from a contaminating bacterium, Pseudomonas fluorescens. The protease only cleaves the GSIII protein at a single site, leaving the oligomer intact but allowing the protein to crystallize in a different space group. This transition from space group P1 to space group C222(1) is accompanied by improved growth characteristics, more reproducible diffraction and enhanced mechanical stability. The crystallographic analyses presented here provide the structural basis of the altered molecular packing in the full-length and digested crystal forms and suggest modifications for future structural studies.
authors.affiliation: Electron Microscope Unit, Department of Molecular and Cell Biology, University of Cape Town, South Africa. jason@science.uct.ac.za
authors.forename: Jason
authors.initials: J
authors.lastname: van Rooyen
authors.forename: Hassan
authors.initials: H
authors.lastname: Belrhali
authors.forename: Valarie
authors.initials: V
authors.lastname: Abratt
authors.forename: B Trevor
authors.initials: BT
authors.lastname: Sewell
mesh_terms: D001441:Bacteroides fragilis / Q000201:enzymology*; D018360:Crystallography, X-Ray; D005974:Glutamate-Ammonia Ligase / Q000737:chemistry* / Q000378:metabolism*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011487:Protein Conformation; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
chemical_list: D005974:Glutamate-Ammonia Ligase